I can Google physical symptoms without getting all hypochondriacal, but when I read about mental illness, I end up wondering if I know anyone sane – including me. For instance, a tendency towards jokiness and the telling of puns runs in my family. Perhaps we have all got a touch of Witzelsucht, a brain disorder that, in one case at least, transformed a lifelong wallflower into the “life of the party.” I had no idea that being happy for no good reason could be pathological, although I’ve often been told to, “wipe that silly grin off your face.” Then there’s…